Large high alloy steel castings are widely used due to it is easy to cast into complex shape steel casting.There are many kinds of large high alloy steel sand castings.Large high alloy cast steel sand castings weight around several tons. The surface of general cast steel high alloy casting is rough and the shape is complex.
Magnetic particle testing for large high alloy steel castings are generally considered as follows:
(1) large high alloy cast steel generally is in large volume and weight and thick wall thickness.It need require to inspect detection of surface and near-surface, therefore it should adopt the single-phase half wave rectifier electromagnetic and dry detection to inspect casting crack,surface under blowhole and slag,etc. The contact method and yoke method can be used in magnetizing method.
(2) due to the large high alloy steel castings with impact of internal stress, some cracks delay cracking, so it should not be detected immediately after casting, but test after one or two days.